Resilient cores with convection barriers particularly for inflatable bodies and methods for making the same

ABSTRACT

Resilient cores preferably for inflatable bodies having resilient slabs that define a plurality of generally columnar holes or resilient arrays of generally columnar solids, methods for making such slabs and arrays, and articles incorporating the same wherein the cores further include thermal transmission mitigation means for improving a core&#39;s resistance to heat transfer beyond the core&#39;s innate insulative properties. Non-exclusive and non-exhaustive examples of such thermal transmission mitigation means in slab core embodiments include consideration to hole or bore geometric cross section, frequency, pattern and orientation, the introduction of a thermal barrier at or within at least some holes or bores, and/or slab material selection/treatment. Non-exclusive and non-exhaustive examples of such thermal transmission mitigation means in array core embodiments include consideration to the geometric cross section, frequency (density), pattern and orientation of the solids, the introduction of thermal barriers within inter-solid spaces and/or solid material selection treatment.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 13/181,420 filed Jul. 12, 2011, which claims the benefit ofPCT/US2009/000206 filed Jan. 12, 2009 and U.S. Provisional PatentApplication Ser. No. 61/010,846 filed Jan. 10, 2008. Each of theaforementioned applications is hereby incorporated by reference as iffully set forth herein.

BACKGROUND OF THE INVENTION

Since the introduction of the original “Therm-A-Rest®” self-inflatingmattress pad in 1971, many improvements regarding the manufacturing andresulting product have been recognized. These improvements have includedmodifications to production methodologies, product durability, productflexibility, and thermal performance. One goal in particular has beenthe reduction in the pad's weight without loss of thermal insulationperformance.

In 1994, Cascade Designs, Inc. (hereinafter “Cascade”) developed a coredmattress pad that could provide a desired level of loft, but included anopen cell core of foam material that had a plurality of laterallyextending hollow cylinders. These transverse cylinders did not affectthe bonding surfaces of the core with the enveloping sheets, butotherwise reduced the overall density of the foam core, and thereforethe weight of the resulting mattress pad. However, manufacturing andperformance issues, as well as the requirement for a relatively thickoriginal core limited the range of applications for this technology.

In 1995, Cascade introduced the “UltraLite” series mattress pads. Thesepads were the first to utilize vertically oriented voids (Le.,orthogonal to the major surface of the core), although these voids werenot the result of a material removal process. For additional informationregarding this technology, please see U.S. Pat. No. 5,705,252, which isincorporated herein by reference.

A significant benefit regarding the technology used in the UltraLiteseries mattress pads was its ability to establish macro voids (asopposed to the open cellular construction of the expanded foam material,which constitutes micro voids) regardless of core thickness. Byorienting the longitudinal axis of the voids in the vertical direction,significant density reduction of the resilient core/slab could beobtained in a relatively thin sectional thickness slab; by selectivelyestablishing the geometry of the voids, the frequency of the voids andtheir overall pattern, otherwise undesirable performance characteristicsof the pad could be minimized.

While the UltraLite core represented a major advance in lightweight coretechnology, it did result in a core having certain manufacturingdisadvantages (e.g., because the voids were formed from displaced slits,and such slits usually were similarly oriented, stability of the corewould be compromised in the direction perpendicular to the displacementbias). In addition, it was recognized that the vertically oriented voidsprovided a convenient convection and radiant heat transmission path,thereby compromising the thermal performance of the mattress pad. It waswith this recognized thermal deficiency that the UltraLite corecontemplated vertical voids that could buckle or collapse uponcompression loading. However, creating voids susceptible to suchcompression buckling also compromised other performance features of thepad, such as core-to-fabric bonding characteristics and vertical supportcharacteristics.

It thus became apparent that voids extending from the bottom to the topof a resilient core could provide a desired reduction in core weightthrough macro density modification without requiring a sectionally thickcore. Moreover, conventional coring techniques, such as die cutting,albeit with material waste, could be used, thereby permitting use ofvarious geometric forms to reduce slab instability that otherwise mayresult from the density reducing actions. However, thermal transmissionmitigation means were needed in order to retain desired performance ofpads incorporating such cores.

SUMMARY OF THE INVENTION

The invention is directed to resilient cores preferably for inflatablebodies comprising resilient slabs that define a plurality of generallycolumnar holes or resilient arrays of generally columnar solids, methodsfor making such slabs and arrays, and articles incorporating the samewherein the cores further comprise thermal transmission mitigation meansfor improving a core's resistance to heat transfer beyond the core'sinnate insulative properties. Non-exclusive and non-exhaustive examplesof such thermal transmission mitigation means in slab core embodimentsinclude consideration to hole or bore geometric cross section,frequency, pattern and orientation, the introduction of a thermalbarrier at or within at least some holes or bores, and/or slab materialselection/treatment. Non-exclusive and non-exhaustive examples of suchthermal transmission mitigation means in array core embodiments includeconsideration to the geometric cross section, frequency (density),pattern and orientation of the solids, the introduction of thermalbarriers within inter-solid spaces and/or solid materialselection/treatment.

As used herein, “slab” with respect to cores, its plural and equivalentscomprises a mechanically unitary structure whether derived from a singleelement or multiple elements, and having a first major surface ingeneral opposing relationship to a second major surface, with a commonperimeter surface joining the two major surfaces; “array” with respectto cores, its plural and equivalents comprises an aggregate structurehaving a plurality of generally columnar solids. “Thermal transmissionmitigation means” comprises intrinsic material (a material compositionderived from the slab or array solids, or derived from material that issubstantially the same as the slab or array solids material) orextrinsic material (a material composition that is not substantially thesame as the slab or array solids material) that is integrated with orinto the slab or array solids, or constitutes a treatment to the slab orarray solids wherein when the core is subjected to opposing compressiveforce in a direction perpendicular to the first and second majorsurfaces, a decrease in thermal transfer rate results through at least aportion of the slab or array that is subject to such compression. Inaddition to the foregoing, the geometric cross section, orientation,frequency, or pattern of holes or bores defined by a slab core or thesolids of an array may be homogeneous or heterogeneous.

Slab core embodiments of the invention may comprise one slab ofresilient material such as expanded foam (preferably urethane) or aplurality of sub-slabs mechanically linked to each other, as will bedescribed in greater detail below. Unless otherwise modified by way ofmaterial treatment, single slab core embodiments are generallyhomogeneous while multi-sub-slab core embodiments may be eitherhomogeneous or heterogeneous. The same is true with respect to arraycore embodiments of the invention: one, some or all solids may comprisea single element of resilient material or a plurality of materialsmechanically linked to each other. Moreover, the interface betweensub-slabs (or array material elements) may be planar or irregular, andoriented in any desired direction, e.g., perpendicular, oblique orparallel to at least one major surface of a slab core embodiment forplanar interfaces.

As noted earlier, slab embodiments of the invention may comprise ahomogeneous slab, or a heterogeneous slab. A homogeneous slab comprisesone that is formed from a singular material having a generallyconsistent average Indentation Force Deflection (“IFD”) value throughoutits volume, regardless of the number of portions, elements, orientationsor zones comprising the slab, i.e., the composition of the slab is notdeterminative of its characterization. A heterogeneous slab comprisesone that has a plurality of zones, each zone having an IFD valuedifferent from an adjacent zone, regardless of the number of portions,elements or zones comprising the slab. A heterogeneous single slab maycomprise multiple IFD zones and/or multiple sub-slabs may comprise acorresponding number of IFD zones. In either homogeneous orheterogeneous slab embodiments, multiple sub-slabs and/or elements areassociated (e.g., bonded, welded) with each other to form a mechanicallink there between. Orientation of such associations (e.g., stacked,adjacent, fitted, spliced, etc.) is not a material constraint of thesedefinitions under most circumstances.

In homogeneous slab embodiments, the slab is characterized as having agenerally consistent average IDF value prior to physical manipulation,such as the creation of holes or contours therein. In such embodiments,therefore, the slab material's otherwise uniform IFD values may beaffected by physical manipulation such as the frequency, placementand/or geometric configuration of the holes, as well as modificationsmade to the sectional thickness thereof such as through shaping.However, the fundamental constitution of the slab remains constant.Slabs comprising at least a pair (a plurality) of sub-slabs withgenerally identical IFD values are included in this class ofembodiments, even if the resulting association modifies the resultingcore's IFD values in certain portions thereof. However, slabs whereinsuch sub-slabs are associated and which purposely exploit theassociation to modify the slab's IFD values for specific reasons are notincluded in this class of embodiments, e.g., an adhesive is used toassociate two sub-slabs and the adhesive cures into a rigid interfacewhose properties are intended to affect the slab's IFD values forintended purposes.

In heterogeneous slab embodiments, factors other than those applicableto homogeneous slab exist to modify the IFD values thereof. Thosefactors include, but are not limited to, associating at least a pair ofsub-slabs having intrinsically differing IFD values (or associatingsimilar IFD sub-slabs wherein the mode or means for associationmaterially and purposefully alters the resulting slab's IFD values asreferenced immediately above); associating at least a pair of sub-slabshaving unique IFD values due to the frequency, placement and/orgeometric configuration of holes, or modifications made to the sectionalthickness thereof such as through shaping; and/or using a single slabhaving intrinsically variable IFD values such as through incorporationof different materials, including a fluid filled reservoir, within theslab.

As noted previously, array embodiments of the invention comprise aplurality of generally columnar solids. The generally columnar solids,which may be arranged in regular and/or irregular patterns, or randomly,include a first portion and a generally opposed second portion, each ofwhich may be separate surfaces or different portions of the samesurface. They are arranged such that the aggregate first surfacesgenerally approximate a first plane and the second surfaces generallyapproximate a second plane. Conceptually then, the first planecorresponds to the first major surface of a slab embodiment, and thesecond plane corresponds to the second major surface thereof. In oneseries of embodiments, the major axes of at least some of the columnsare generally perpendicular to the virtual first and/or second planes.These types of columns are referred to herein as “normal columns”. Inanother series of embodiments, the major axes of at least some columnsare generally not perpendicular to the virtual first and/or secondplanes. These are referred to herein as “oblique columns”.

With respect to slab core embodiments of the invention and as disclosedabove, a plurality of holes or bores are defined by the slab (unlessotherwise indicated or obvious from the context of usage, the term“slab” will hereinafter refer to single or multiple sub-slabs whetherhomogeneous or heterogeneous). The axes of holes perpendicular to thefirst major surface of the slab, perpendicular to the second majorsurface of the slab, or perpendicular to both major surfaces arereferred to as “normal holes/bores”. The axes of the holes/bores mayalso be acute to the first and/or second major surfaces. In other words,the point of hole axis intercept with the first major surface is not indirect opposition to the point of hole axis intercept with the secondmajor surface. Generally, such holes or bores are referred to as“oblique holes/bores”. In addition to axis orientation, the holes/boresdefined by a slab core include a geometric cross section, frequency andpattern. As will be described in detail below, the geometric crosssection may be exploited as a form of thermal transmission mitigationmeans. Parameters concerning frequency and pattern also core density,performance, insulation value distribution and other factors that willalso be described in detail below.

With respect to oblique hole/bore embodiments of the invention, suchholes/bores are divided for purposes of discussion into two species:“open” and “occluded”. Open holes/bores are those that have not physicalimpediments to matter transit from one hole/bore orifice to the other ina direction orthogonal to the first or second major surface (which everis gravitationally closer to the earth's surface); occluded holes/boreare those that do have a physical impediment to matter transit in adirection orthogonal to the first or second major surface (both holespecie are open in the sense of having a through passage from oneorifice to the other, but when viewed in section and along a directionorthogonal to the gravitationally lower major surface, open embodimentswill have a non-occluded passage while occluded embodiments have such anorientation/geometry that orthogonal matter transit will necessarilyimpinge upon a hole/bore wall prior to exiting from an opposingorifice).

Thermal transmission mitigation generally comprises means of varyingeffectiveness to mitigate conductive, convective and/or radiant thermaltransfer. Because conductive thermal transfer is not a major mode ofheat transfer in embodiments of the invention due to the presence of thecore separating opposing major surfaces, focus is made with respect toconvective and radiant means for thermal transmission mitigation.

A principle means for creating a convection thermal barrier is tointerrupt fluid/gas movement or currents within a volume, as is wellknown. Core embodiments of the invention comprise holes/bores in slabcores and/or inter-solid spaces in array cores. Thus, in addition tofactors concerning thermal permeability of the core, the holes/bores andspaces provide a particularly important conduit for heat transfer fromone “surface” of the core to the opposing, surface. Similarly, theholes/bores and spaces within a core can become the primary conduit forradiant heat transfer. Thus, placement of suitable thermal transmissionmitigation means in the holes/bores and/or spaces or at one or bothorifices of a hole/bore represents an effective mode for achieving thestated objective of the thermal transmission mitigation means.

Turning first then to the normal or perpendicular hole/bore slab coreembodiments of the invention, it is desirable to provide some form ofthermal mitigation means at an orifice of, and/or in, at least some ofthe holes/bores to reduce at least convective thermal transfer therethrough, and preferably also radiant thermal transfer. Thus, theseembodiments will preferable include a discrete plug member disposed inat least some of the holes/bores, and/or will preferably have a thermalbarrier such as a sheet material at one or both major surfaces toocclude at least some of the open holes/bores. Where at least twosob-slabs comprise the slab, the thermal transmission mitigation meansmay also be disposed at the interface between sub-slabs, and ispreferably a sheet material.

Open oblique holes/bores in slab core embodiments of the inventionsimilarly benefit from the thermal transmission mitigation meansapplicable to open normal holes/bores. However, the benefits obtained byproviding separate thermal transmission mitigation means for normal oropen oblique holes/bores are not as significant when oblique occludedholes/bores are involved. Because convective thermal transfer generallyoccurs in a direction that is congruent, but opposite in direction, togravitational acceleration, at least a portion of the slab corefunctions to mitigate thermal transmission (since a body supporting matsupporting surface is usually (or at least preferably) orthogonal tosuch directions, providing for a hole/bore that is occluded in thisdirection inherently provides a convection mitigation means, althoughadditional insulation may be desired). Thus, the treatment of a slabcore to define at least one oblique occluded hole/bore itselfconstitutes a form of thermal transmission mitigation means forimproving a core's resistance to heat transmission beyond its innateinsulative properties.

A benefit realized from the incorporation of oblique holes/bores(whether open or occluded) is that they are more susceptible toorthogonally oriented compression deformation (buckling/collapsing dueto application of compressive forces in a direction that isperpendicular to at least one major surface) than holes/bores havingsimilar geometric cross section that are considered “normal” to at leastone major surface. During compression buckling/collapsing of an obliquehole/bore, it necessarily becomes occluded or more occluded.Consequently, the insulative property of such a slab core is increasedthrough its use: all of the advantages available through the use of aperforated core (one having a plurality of holes/bores) are realizedwith the oblique column body embodiments, yet the primary thermaldeficiency, namely convective heat transfer through the holes/bores, isgreatly mitigated at least in portions of the resulting structuresubject to compression loading.

In embodiments having plug members, the plug members need not occupyeach hole/bore, but in certain embodiments do so. Plug members may bepositioned anywhere within a hole/bore since occlusion between the twoorifices defining the boundaries of the hole/bore is an objective.However, for manufacturing purposes, it may be desirable to have suchplug members positioned near one or both major surfaces of a slab/core.Preferably, the plug members are formed from the material removed fromthe slab/core to form the holes/bores, but may also be waste materialfrom other operations such as batting remnants and the like.Additionally, to retain the benefits of core weight, which is aprinciple reason for hole/bore creation, the plug member is preferablyless dense than the slab core material and/or occupies less volume thanthe hole/bore into which it resides.

In other slab core embodiments, thermal convention heat transfer ismitigated by positioning a sheet material, such as a film, a thin foammaterial or a batting preferably constructed from polyester, over one orboth major surfaces. If a final structure such as a self-inflating padhaving tensile elements therein is desired, then it may be desirable toselectively apply or establish an adhesive or low molting point plastic.to such sheet material. In this manner, the sheet material may be bondedor adhered to the slab/core, as well as any enveloping structure.

In many embodiments, the other form of heat transfer referenced above isaddressed, in addition to or in lieu of convection transmissionmitigation means. To address radiant heat transfer modes, the core maysubjected to a surface treatment of a radiant reflecting material, e.g.,vapor deposited aluminum, or a radiant barrier film may be associatedwith one or both major surfaces. Again, depending Upon applications, itmay be desirable to selectively apply or establish an adhesive or lowmelting point plastic to such film material, if such properties are notalready inherent. Such films, which are well known in the industry,comprise an aluminized MYLAR® or other form of polymeric film materialhaving a highly thermally reflective coating on one or both sidesthereof. If such films are positioned on both sides of a slab core, thenprovisions may be made for venting gas/fluid from the columns if theslab core is not sufficiently fluid/gas permeable. if the perimeter ofthe slab/core is exposed to the environment (e.g., it is not bonded toany impervious material) and if the slab core has intrinsic gas/fluidmigration properties (e.g., open cell foam), then it is not necessary,although perhaps desirable, to perforate at least one film to permitappropriate gas/fluid escape and entry.

In addition to being associated with one or both major slab coresurfaces, both convection and/or radiant transmission mitigation meanscan be disposed between two or more sub-slabs comprising a slab core.Again, because the purpose of the mitigation means is to interrupt heattransfer from one side of the slab/core to the other side, the preciseposition or location thereof is not critical to the desired performanceof the core. Moreover, this form of thermal transmission mitigationmeans finds utility not only with normal holes/bores but also withoblique open or occluded holes/bores. In particular, film-based radiantbarriers improve overall performance of any slab core configuration.

Slab core invention embodiments having at least two verticallyassociated (stacked) slabs comprising a slab core can also employ ahole/bore offset arrangement as a viable thermal transmission mitigationmeans for improving a core's resistance to heat transmission,particularly regarding convection transfer. In these embodiments,holes/bores in a first sub-slab are offset from holes/bores in as secondsub-slab such that the path from one hole/bore orifice to another isoccluded. In other words, the holes/bores are at least partiallydiscontinuous through the section of the slab core, and thus retain thebenefits of a perforated slab/core, yet mitigate thermal convectionthere through. As with other embodiments, this feature can be exploitedin both normal hole/bore embodiments of the invention as well as obliqueopen or occluded forms.

The foregoing discussion concerned the constitution of slab and arraycores. However, advantageous thermal mitigation can also be achievedthrough appropriate selection of materials for the envelope of aninflatable body, which constitutes a preferred exploitation of the coresof the invention. As stated previously, the envelope for an inflatablebody using any of the core embodiments of the invention may be wholly,substantially, partially, or selectively bonded to the core eitherdirectly or indirectly, or may not be bonded thereto at all. As such,increased thermal performance (i.e., decreased thermal transmission fromone side of the core to the other) can be achieved by integratinginsulating materials into or treatment of the envelope material,particularly when the envelope is at least partially or selectivelybonded to the core. Examples include convection and/or radiant barriersassociated with the envelope material (either externally to be exposedto the environment or internally to be exposed to the core, or as anintermediate layer between a layer exposed to the environment and alayer presented to the core). Given the nature of the materialcomprising the envelope, preferred embodiments will include an envelopehaving a radiant barrier.

While many of the forgoing invention embodiments can be constructed by apractitioner having ordinary skill in the art without undueexperimentation, cost effective construction techniques for slabs havingoblique columns has been elusive. One solution has been to create normalholes/bores in a slab having a sectional thickness much greater thandesired, and then removing a portion there from that has parallelopposing major surfaces and oblique columns. This solution, however,generates great waste and introduces other technical problems. Anothersolution has been to use oblique cutting tools. Again, however,specialized equipment is necessary and such techniques do not lendthemselves to volume production.

A solution utilized in construction of invention embodiments having sucha slab core uses tools intended for forming normal holes/bores. However,rather than simply applying the tools to a slab or orthogonallycompressing the slab's major surfaces, an orthogonally compressed slabis subject to shear force. In other words, when such friction betweentwo compression platens, for example, has been established, the platensare differentially shifted so as to induce sheer in the slab. At thispoint, the slab can be perforated in a direction orthogonal to theplatens in order to establish the desired column frequency andpattern(s). Upon release of the platens, the slab resumes its restinggeometry, but now defines a plurality of oblique columns. The degree ofdifferential movement will determine the relative hole/bore orientation,including the creation of oblique occluded holes/bores.

For purposes of this patent, the terms “area”, “boundary”, “part”,“portion”, “surface”, “zone”, and their synonyms, equivalents and pluralforms, as may be used herein and by way of example, are intended toprovide descriptive references or landmarks with respect to the articleand/or process being described. These and similar or equivalent termsare not intended, nor should be inferred, to delimit or define per seelements of the referenced article and/or process, unless specificallystated as such or facially clear from the several drawings and/or thecontext in which the term(s) is/are used.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a conventional slab core wherein aplurality of open normal holes/bores extending from one major surface toan opposing major surface are defined by a slab of resilient material;

FIG. 2 is a detailed partial section view of the slab core of FIG. 1illustrating unrestricted radiant and convection thermal transmissionpaths provided by normal holes/bores;

FIG. 3 shows the slab core of FIGS. 1 and 2 after incorporation of athermal transmission mitigation means in the form of discrete plugmembers disposed in at least some of the normal holes/bores, accordingto an embodiment of the invention;

FIG. 4 illustrates a variation of the slab core of FIGS. 1 and 2 whereinthe slab comprises two sub-slabs and wherein a thermal transmissionmitigation means in the form of a thermal barrier is disposed therebetween, according to an embodiment of the invention;

FIG. 5 is a perspective view of an array core embodiment of theinvention wherein a plurality of columnar solids are shown in registeredopposition and a thermal transmission mitigation means in the form of athermal barrier is disposed there between;

FIG. 6 is a perspective view of a slab core embodiment of the inventionwherein a plurality of occluded oblique holes/bores extend from onemajor surface to an opposing major surface of a slab of resilientmaterial to constitute a thermal transmission mitigation means;

FIG. 7 is a detailed partial section view of the slab core of FIG. 6illustrating the occluded nature of the oblique holes/bores, thusconstituting a radiant heat transmission mitigation means;

FIG. 8 shows the section view of FIG. 7 after the slab core is subjectedto an orthogonal compressive load, thereby collapsing at least someoccluded oblique holes/bores and constituting a convection heattransmission mitigation means;

FIG. 9 is a perspective view of a slab core embodiment of the inventionwherein a thermal transmission mitigation means in the form of aplurality of open normal holes/bores extend from one major surface to anopposing major surface of a slab of resilient material and havepurposely selected geometric cross sections to decrease the forcenecessary to achieve compression collapse of the same;

FIG. 10 is a cross section view taken substantially along the line 10-10in FIG. 9 showing several of the holes/bores prior to compressionloading;

FIG. 11 shows the cross section of FIG. 10 after subjected tocompression loading in a direction orthogonal to the major surface ofthe slab core whereby the several holes/bores constitute a convectionheat transmission mitigation means;

FIG. 12 is an exploded schematic view in perspective of a slab coredisposed between an upper platen and a lower platen;

FIG. 13 shows the arrangement of FIG. 12 after platen compression of theslab core;

FIG. 14 is a representative side elevation view of the arrangement shownin FIG. 13;

FIG. 15 is a detailed partial cross section view of the arrangementshown in FIG. 14;

FIG. 16 shows the lateral movement of an upper platen in compressivecontact with the slab core to induce shear therein, and the applicationof die elements to create holes/bores therein;

FIG. 17 shows the die elements of FIG. 16 fully extended into the slabcore;

FIG. 18 shows the arrangement of FIG. 17 after removal of the dieelements; and

FIG. 19 shows the arrangement of FIG. 18 after disengagement of theplatens and restoration of the original form of the slab core, which nowpossess occluded oblique holes/bores.

DESCRIPTION OF INVENTION EMBODIMENTS

Preface: The terminal end of any numeric lead line in the severaldrawings, when associated with any structure or process, reference orlandmark described in this section, is intended to representativelyidentify and associate such structure or process, reference or landmarkwith respect to the written description of such object or process. It isnot intended, nor should be inferred, to delimit of define per seboundaries of the referenced object or process, unless specificallystated as such or facially clear from the drawings and the context inwhich the term(s) is/are used. Unless specifically stated as such orfacially clear from the several drawings and the context in which theterm(s) is/are used, all words and visual aids should be given theircommon commercial and/or scientific meaning consistent with the contextof the disclosure herein.

The following discussion is presented to enable a person skilled in theart to make and use the invention. Various modifications to thepreferred embodiment will be readily apparent to those skilled in theart, and the generic principles herein may be applied to otherembodiments and applications without departing from the spirit and scopeof the present invention as defined by the appended claims. Thus, thepresent invention is not intended to be limited to the embodiment show,but is to be accorded the widest scope consistent with the principlesand features disclosed herein.

Turning then to the several drawings wherein like numerals indicate likeparts, and more particularly to FIGS. 1 and 2, a conventional slab coreis shown for reference. Slab core 20 is preferably formed from aresilient material, which is often an open cellular foam material andparticularly an open cellular urethane foam. Slab core 20 has majorsurfaces 22 and 24 (for convention, major surface 22 may also bedescribed herein as “lower major surface 22” and major surface 24 mayalso be described herein as “upper major surface 24”; major surface 24is not shown in the perspective views but is necessarily present and isreferenced for completeness), as well as perimeter surface 26. Slab core20 further defines a plurality of holes/bores 30, which are generallybounded by orifices 32 and 34 (orifices 34 are not shown as they arepresent on major surface 24), and by wall 36. Each hole/bore 30 has ageometric cross section.

As particularly illustrated in FIG. 2, holes/bores 30 have a major axisthat is generally orthogonal to both major surfaces 22 and 24, and aretherefore styled as “normal holes/bores”. Also as particularlyillustrated in FIG. 2 is the lack of any thermal transmission mitigationmeans to affect the rate of radiant or convection heat transfer betweenmajor surfaces 22 and 24. Thus, while creating a less dense slab core,introduction of holes/bores 30 decreases the innate insulative propertyof the slab core.

A first illustrated solution to undesired loss of insulative propertiesin such slab cores is shown in FIG. 3 wherein a plurality of plugelements 40 are introduced into, or are retained in during formation of,at least some of holes/bores 30. Whether derived from intrinsic orextrinsic material, whether linked to a common substrate or discrete innature, plug elements 40 are disposed between opposing major surfaces 22and 24 to limit convective and/or radiant heat transfer there between.The skilled practitioner will appreciate that material selection forplug elements 40 will affect insulative performance of the slab as wellas weight. Therefore, the balance between these two factors will atleast partially drive the material selection process.

A second illustrated solution to undesired loss of insulative propertiesin such slab cores is shown in FIG. 4 wherein thermal barrier 50 isdisposed between two sub-slabs 20′a and 20′b, which combined form slabcore 20′. Thermal barrier 50 again may comprise any material intendedfor its purpose. Thus, many embodiments within this solution will useradiantly reflective batting such as aluminized MYLAR® (a film material)or polyester batting (generally a spun material) so that both radiantand convection heat transfers modes will be beneficially affected.Alternatively or additionally, thermal barrier 50 may be disposed oneither or both major surfaces 22 and 24, again with consideration beinggiven to the competing objectives of decreasing slab core weight andimproving thermal performance. Thermal performance can further beincreased in multi sub-slab embodiments by offsetting holes/bores 30 inaddition to integrating thermal barrier 50 therein.

Thermal barrier 50 can also be used as a substrate for columnar solids160 to create array core 120, as best shown in FIG. 5. Here, both sidesof barrier 50 have solids 160 associated there with, preferably beingmechanically linked thereto such as by adhesive or similar means.

In addition to adding material to a slab core 20/20′ as a form ofthermal transfer mitigation means, slab core 20 can be treated.Treatment can comprise application of chemicals or other substances, orcan comprise modification of the hole/bore parameters. As best shown inFIGS. 6-8, oblique occluded holes/bores 230 can be formed in slab core220. Such holes/bores intrinsically mitigate radiant heat transfer,which is linear and nearly always orthogonal to one or both majorsurfaces 222, 224; the radiation entering an orifice 232, 234 willnecessarily impinge upon a hole/bore wall 236. However, there stillexists an effective fluid path between orifices 232 and 234, which isconducive to convection heat transfer.

A feature of many oblique holes/bores, whether open or occluded, istheir tendency to collapse during off axis compression, as best shown inFIG. 8. When in a collapsed state, the previously open fluid pathwaydefined by walls 236 is now obstructed, thereby significantly reducingheat transfer via convection, and greatly improving thermal performanceof the slab core, without the addition of any intrinsic or extrinsicmaterial. Because in many applications such as inflatable paddingthermal performance is only of issue when such articles are undergoingcompression, the selective closure of such convection pathways is notdetrimental.

While oblique holes/bores are considered desirable, normal holes/borescan be created to include similar functionality, albeit with perhapsreduced performance. FIGS. 9-11 demonstrate a similar hole/bore collapsestrategy whereby normal holes/bores 330 are formed in slab core 320, andundergo compressive collapse to thereby obstruct the previously openfluid pathway defined by walls 336. The skilled practitioner willappreciate that intelligent selection of the geometric cross section ofany given hole/bore and awareness of hole/bore density within the slabcore will affect the force necessary to achieve collapse as well as thereduction in slab core weight.

Turning next to FIGS. 12-19, a method for creating slab core 230 isillustrated. A solid slab 230′ is positioned between two foraminousplatens 270 a and 270 b (FIG. 12) and compressed thereby (FIGS. 13-15)with sufficient force to generate a coefficient of friction sufficientto permit slab 230′ to undergo shear as best shown in FIG. 16. At suchtime, die elements 280 enter through holes 272 a in platen 270 a,perforate slab 230′ and partially exit through holes 272 b in platen 270b, as is shown in FIG. 17. Upon withdrawal of die elements 280 (FIG. 18)and decompression of platens 270 a and 270 b (FIG. 19), the shear forceis removed from slab 230, which reverts to its original configuration.The resulting slab 230 now possesses oblique holes/bores 230 that werecreated by non-obliquely aligned tools.

What is claimed is:
 1. A method of creating a resilient core ofmaterial, comprising the steps of: positioning a slab between first andsecond platens; compressing the slab with the platens with sufficientforce to generate a predetermined coefficient of friction between theslab and platens; moving the first platen in a direction parallel to thesecond platen thereby causing the slab to undergo shearing deformation;after moving the first platen in a direction parallel to the secondplaten, perforating the slab with die elements; withdrawing the dieelements from the slab; and removing the slab from between the platens.2. The method of claim 1, wherein at least one of the first and secondplatens is foraminous.
 3. The method of claim 1, wherein the slab ismechanically unitary.
 4. The method of claim 1, wherein perforating theslab with die elements comprises inserting the die elements throughholes in the first and second platens.